Rather than trying to be all witty about Easyjet's helpdesk, you can start by checking their website about their rules and regulations on flying with children/infants and which happens to be quite comprehensive (if you take your time to actually read it):

It's your responsibility to ensure that your car seat qualifies as acceptable or not according to below two requirements from Easyjet:

•able to fit in the 42cm space between the arm rests on the aircraft seats
•upright and forward facing (For safety reasons, a backward facing seat cannot be used when the fasten seat belt sign is on. So, unless your infant will be sitting on your lap at these times, they must be the right age for a forward-facing seat).

You can't expect a call center employee or anyone on the planet for that matter to know all types of car seats available on the market, hence the stipulations above apply for all Easyjet flights.

The Easyjet website further states that "Only 2 infants are allowed with every one accompanying adult" and "If you wish any infant under 2 to have their own seat you will need to bring a car seat to use on the plane."

So long story short if you decide to take a Maxi Cosy type 45 cm wide "upside facing" car seat then you are at risk of not being allowed to use it, as simple as that.

It can then go into the hold of the plane but then your wife is left with two infants on her own, which she can't/won't be allowed to take both on her lap.

The following 4 users would like to thank donpiedro for this useful post: